Peace and Myakka River Water Quality Summary 2002 - Southwest ...

The Estuary Program plans to release a report summarizing the results of thoseanalyses during 2002.WATER QUALITY IN NON-TIDAL (FRESHWATER) AREASA water quality index (WQI) developed for Florida streams by FDEP was used tosummarize existing water quality conditions at the non-tidal stations monitored by thecooperative program during water years 1998-2001.The WQI was developed using sampling data collected in 1987 from 2,000 streammonitoring sites throughout the state. Based on those data, percentile distributions ofseveral groups of water quality indicators — including nutrients, water clarity, dissolvedoxygen and oxygen-demanding substances — were determined on a statewide basis.WQI values are calculated using those percentile distributions: for example, a stationwith an average annual total nitrogen concentration of 1.2 mg/L — the median valueobserved in the 1987 data set — would receive a WQI score of 50 (denoting the 50 thpercentile) for that indicator.Overall WQI scores can be averaged across indicator categories to obtain an averageindex value for each monitoring site. FDEP guidelines suggest that average indexvalues of 0-44 indicate “good,” 45-60 indicate “fair,” and >60 indicate “poor” waterquality conditions in Florida streams.For this study, annual average WQI values were calculated using five water qualityconstituents (turbidity, total suspended solids, total organic carbon, nitrate+nitritenitrogen, and total nitrogen). A total of 58 annual average WQI values were calculatedfor the 16 stations sampled during water years 1998 - 2001.The Saddle Creek at Structure P-11 station, which is located immediately downstreamfrom Lake Hancock in the upper Peace River basin, exhibited the poorest water qualityamong the sites sampled, falling in the 75th to 95th percentiles of Florida streams formost parameters in each year.Other monitoring sites at which “poor” water quality conditions were observed included:• Peace Creek Canal near Wahneta (in water years 1998 and 1999),• Peace River at Bartow (1998, 1999)• Peace River at Ft. Meade (1998)• Peace River at Zolfo Springs (1998)• Peace River at Arcadia (1998)• Big Slough Canal near Myakka City (2000).Two sites exhibited consistently “good” water quality based on the WQI:• Shell Creek near Punta Gorda (1998-2001)• Myakka River at Myakka City (1999-2001).iv